Fibrous histiocytoma refers to a type of growth that can develop in various parts of the body, frequently involving the skin or soft tissues. These growths originate from cells involved in tissue repair and inflammation. While most fibrous histiocytomas are non-cancerous, a rare subset can be malignant.
Understanding Fibrous Histiocytoma
Fibrous histiocytomas encompass a range of lesions, with dermatofibroma (benign fibrous histiocytoma of the skin) being the most common. This non-cancerous skin lesion typically appears as a firm, small, brownish or reddish nodule, arising from a proliferation of fibroblasts and histiocytes.
Historically, “Malignant Fibrous Histiocytoma” (MFH) was a term for a malignant form. Medical classification has evolved, reclassifying most lesions previously called MFH. They are now primarily recognized as Undifferentiated Pleomorphic Sarcoma (UPS) or other specific sarcomas, based on distinct cellular and genetic profiles.
UPS is a rare, aggressive soft tissue sarcoma, a cancer developing in supporting tissues like fat, muscle, and nerves. While “MFH” may still appear in older literature, the medical community now uses precise classifications like UPS for these malignant tumors. This distinguishes them from the common, benign dermatofibroma.
Recognizing Symptoms and Appearance
Fibrous histiocytomas present differently depending on whether they are benign or malignant. Benign dermatofibromas usually appear as small, firm, reddish-brown to purplish bumps on the skin, often on legs, arms, or back. A characteristic “dimpling sign” occurs when the center indents inward when squeezed.
Dermatofibromas are usually painless, though some report mild itching or tenderness if irritated. They grow slowly or remain stable. Their distinct appearance often allows for preliminary visual identification.
In contrast, malignant UPS presents differently. These tumors often manifest as a rapidly growing lump or mass, frequently deep within soft tissues rather than on the skin surface. They can occur in various locations, including the extremities, trunk, or retroperitoneum. These malignant growths may or may not be painful, and their size can vary considerably.
Diagnosis and Evaluation
Diagnosis begins with a thorough physical examination by a healthcare professional, assessing the growth’s appearance and feel. The doctor also gathers patient history, inquiring about its onset, growth rate, and any associated symptoms like pain or itching.
A biopsy is always necessary for a definitive diagnosis. For suspected benign skin lesions like dermatofibromas, a skin biopsy is typically performed. If a malignant tumor like UPS is suspected, an incisional or core needle biopsy is often preferred to obtain sufficient tissue. The sample is then sent to a pathologist.
A pathologist reviews the biopsy sample under a microscope to identify cell types, their arrangement, and abnormal features, determining if the growth is benign or malignant and its classification. For suspected malignant cases, imaging tests are significant. MRI assesses the tumor’s size, depth, and relationship to surrounding structures, while CT or PET scans may check for potential spread.
Treatment Options
Treatment for fibrous histiocytomas depends on whether the growth is benign or malignant. Benign dermatofibromas often require no treatment. They are harmless and typically left alone unless they cause persistent itching, pain, irritation, or are a cosmetic concern. If removal is desired, simple surgical excision is the primary treatment. Cryotherapy or laser therapy may also be considered.
In contrast, malignant UPS necessitates an aggressive treatment strategy. The primary treatment for UPS is wide surgical excision, removing the tumor along with a margin of healthy surrounding tissue to ensure all cancerous cells are removed. The extent of the surgical margin depends on the tumor’s size, location, and proximity to important structures.
Adjuvant therapies are often employed to reduce recurrence or metastasis risk. Radiation therapy may be administered before or after surgery to target remaining microscopic tumor cells. Chemotherapy might be considered for large, high-grade tumors, or if cancer has spread. Treatment combinations are tailored to each patient based on tumor characteristics, stage, and overall health.
Outlook and Monitoring
The outlook for fibrous histiocytomas varies considerably, depending on whether the growth is benign or malignant. For benign forms like dermatofibromas, the prognosis is excellent. These non-cancerous lesions pose no threat to health. After surgical removal, they typically do not recur in the same spot, though new ones can develop elsewhere.
For malignant UPS, the prognosis is more variable, depending on factors like tumor size, histological grade, location, and whether it has spread. Smaller, lower-grade tumors completely removed tend to have a better outlook.
Regular follow-up appointments are an important part of UPS management. These typically involve physical examinations and imaging scans (MRI, CT, X-rays) at scheduled intervals. This monitoring helps detect local recurrence or distant metastases early, allowing for prompt intervention and comprehensive treatment.